The seat of the Tribunal is in the Free and Hanseatic City of Hamburg in the Federal Republic of Germany. In 1986, Germany offered to provide premises for the Tribunal at the expense of the Federal Government, including a substantial contribution from the City of Hamburg.

An architectural competition was held in 1989 to select the design of a suitable building to house the Tribunal. The first prize was awarded to the firm of Baron Alexander and Baroness Emanuela von Branca. The foundation stone of the permanent headquarters was laid on 18 October 1996 at the site on the Elbchaussee in Nienstedten, overlooking the river Elbe. Pending construction of the headquarters, temporary premises were made available to the Tribunal as of its first session in October 1996.

The joint ceremony of the Tribunal, the Government of the Federal Republic of Germany and the Senate of the Free and Hanseatic City of Hamburg for the official opening of the permanent premises of the Tribunal took place on 3 July 2000. At the ceremony, statements were delivered by the Secretary-General of the United Nations, Mr. Kofi Annan; President Chandrasekhara Rao; the Federal Minister of Justice of the Federal Republic of Germany, Mrs. Herta Däubler-Gmelin; the First Mayor of Hamburg, Mr. Ortwin Runde; and Registrar Chitty. The ceremony was attended by the Vice-President and other judges of the Tribunal and high dignitaries, including the President of the Meeting of States Parties, Mr. Peter Donigi; the Legal Counsel of the United Nations, Mr. Hans Corell; Ministers and other Government representatives and representatives of international organizations.

The Agreement between the Tribunal and the Government of the Federal Republic of Germany on the Occupancy and Use of the Premises of the International Tribunal for the Law of the Sea in the Free and Hanseatic City of Hamburg (Additional Agreement) of 18 October 2000 establishes the terms and conditions under which the premises are made available by the Government to the Tribunal.